Field of the Invention
The present invention relates to a touch sensitive display device, and more particularly to, a multi-touch sensitive display device and a method for assigning a touch identification in the multi-touch sensitive display device.
Discussion of the Related Art
A user interface (UI) is configured so that users are able to communicate with various electronic devices and to easily and comfortably control the electronic devices as they desire. Examples of user interfaces include, but not limited to, a keypad, a keyboard, a mouse, an on-screen display (OSD), and a remote controller having an infrared communication function or a radio frequency (RF) communication function. User interface technology has continuously expanded to increase the user's sensibility and handling convenience. More recently developed user interfaces include a touch UI, a voice recognition UI, a 3D UI, and so on.
The touch UI has been widely adopted in portable information devices, such as smart phones, and its use has been expanded to notebook computers, computer monitors, and home appliances. A touch screen having capacitive touch sensors detects a touch input by sensing changes in capacitance (i.e., changes in the amount of charges in the touch sensors) when a user touches a touch sensor or sensors with his or her finger or another pointer.
Recently, as display devices become larger in size, an interest in a multi-touch sensitive display device capable of simultaneously recognizing a plurality of touch inputs is increasing. A multi-touch sensitive display device divides a plurality of touch inputs received from a plurality of users using identification (ID) tracking technology and then performs an operation of matching touch IDs of a current frame to touch IDs of a previous frame. Touch coordinates of the same user, which may repeatedly change during a plurality of frame periods, may be connected to the same touch ID through such a touch ID assignment operation.
A related art touch ID assignment technology compares touch points of an n-th frame (where n is a positive integer greater than 1) with touch points of an (n−1)-th frame, prioritizes the touch points, and connects each of the touch points of the n-th frame to a touch ID of the (n−1)-th frame having a relatively high priority. Because the related art touch ID assignment technology has to compare connectivity between all of the touch points of the touch screen, a process time required to assign the touch ID increases when the number of touch points increases. Hence, a touch report rate decreases, and the touch latency performance suffers.
As shown in FIGS. 1 to 3, a method for reducing an area of comparison objects to adjacent touch groups has been proposed to solve the above-described problem. The proposed related art method divides touch inputs into previously set touch groups and compares touch points of each touch group with all of the touch IDs of the adjacent touch groups. In FIG. 1, small rectangles with shading indicate the touch points. In FIGS. 1 and 2, the second, the seventh to the ninth, and the twelfth to the fourteenth groups GP2, GP7-GP9, and GP12-GP14 each have the touch points. In FIG. 2, the group having the touch points is denoted by a circle.
The number of touch points belonging to the second group GP2 is five, and the total number of touch points belonging to the adjacent groups GP1, GP2, GP6, GP7, and GP8, which are compared with the second group GP2, is ten. The total number of touch points in the second group GP2 and its adjacent groups is 15. Thus, the number of comparison processes for assigning the touch points of the second group GP2 to a touch ID is 255 (=15*15). In the same manner as the second group GP2, the number of touch points belonging to the eighth group GP8 is five, and the total number of touch points belonging to the adjacent groups GP2-GP4, GP7, GP9, and GP12-GP14, which are compared with the eighth group GP8, is 28. The total number of touch points in the eighth group GP8 and its adjacent groups is 33. Thus, the number of comparison processes for assigning the touch points of the eighth group GP8 to the touch ID is 1089 (=33*33).
The proposed related art method compares adjacent touch groups, instead of the entire area of the touch screen, and can therefore reduce the area of the comparison objects. However, when a large number of adjacent touch groups (i.e., a large number of comparison touch groups) are used and the touch points are concentrated on the comparison touch groups (for example, the group GP1 of FIG. 3), it is difficult to reduce the process time.
When the touch report rate decreases and the touch latency performance suffers, it is difficult to implement a fast response to a touch input.